Already known from Swiss patent CH 594 924 is a push button for timepieces comprising a stem, a return spring and a moisture seal, the whole being inserted in a guide socket intended to be secured in the case of a timepiece. The portion of the socket situated on the interior of such case ends with an opening bounded by an annular flange of tapered form. This flange is elastic and permits the passage through the opening of the end portion of the stem. Such end portion exhibits an outer diameter substantially greater than the diameter of the opening. Thus the stem may be axially positioned in the socket, the return spring being concentrically arranged on the stem and being directly supported on the moisture seal, the latter being confined between the spring and the end flange of the socket.
This construction operates in a satisfactory manner but exhibits in particular the difficulties of requiring a number of manipulations and pre-assembly operations which render impossible the manufacture of such push buttons at a low price.
The push button described in the Swiss patent CH 621 453 constitutes an attempt to overcome the difficulties cited above.
This push button includes a stem in three parts, a return spring and a moisture seal arranged directly in a hole provided in a wall of a support receiving the push button. The hole opens into the interior of the support through a constriction. The inner portion of the stem passes through such constriction and terminates with a flange having a cylindrical exterior surface with a diameter substantially greater than the diameter of the constriction this inner portion being axially split. Thus, when the stem is inserted in the hole in the wall, the inner portion with its flange is radially deformed by elastic squeezing at the passage of the constriction, after which it reassumes its initial form, the flange assuring axial maintenance of the stem.
This construction has the advantage of eliminating the utilization of the guiding socket provided in the construction proposed in Swiss patent CH 594 924. Nevertheless, it still presents certain difficulties. Effectively, a stem in three portions as in the Swiss patent CH 621 453 must be machined on a profiling lathe and in order thereafter to machine the axial slot in the inner portion of the stem, it is necessary to stop the lathe and to employ a special tool. There thus results an increase in the time and the cost of manufacture.
Furthermore, the machining of such a slot brings the risk of forming burrs which may hinder the putting into place of the stem such that there must be provided an additional operation of burr removal.
The invention thus has as its purpose to overcome the difficulties brought about by the prior art and to furnish a push button which is simple to obtain and easy to assemble.